(1) Field of the Invention
The invention relates to a test valve assembly adapted to be incorporated in a tubing or drill pipe string lowered from a drilling vessel or platform to dispose the lower portion of the string in an underwater or subsea well bore and the test valve assembly in a subsea blowout preventer stack which is suitably activated to close around the assembly.
(2) Description of the Prior Art
After the drilling of a subterranean oil or gas well at an offshore location and through a subsea well bore, it may be necessary or desirable to run on the drill string a series of drill stem or other testing equipment which may be activated or manipulated by rotation of the drill string. For example, inflatable straddle test tools are carriable on the drill string and are anchored on and sealed against the inner wall of the casing. Such equipment is inflatable to anchored and sealed relationship with the casing by rotating the drill pipe to, in turn, activate a mud pump for inflation of the packing mechanism. Since control of the well through the drill string must be maintained during the testing procedure, an apparatus having a manipulatable safety valve mechanism therein must be carried on the drill string above the test equipment for manipulation to the closed position while the well is being tested. In instances in which inflatable test tools, as described above, are utilized, the use of conventional and prior art safety valves, incorporated in a "test tree" valve assembly, such as that illustrated in U.S. Pat. No. 3,568,715, entitlted "Well Tools," Donald F. Taylor, Jr., inventor, is unsatisfactory because of the utilization of an exterior hydraulic control line which is necessary to manipulate the ball or other valving mechanism between open and closed positions, the hydraulic line extending from a control panel on the drill ship or semi-submersible, exterior of the entire length of the drill string to the "test tree," and the ball or other valve mechanism. Additionally, such hydraulically activated valve mechanisms also incorporate latching mechanisms which have been partially or completely activated by utilization of the exterior hydraulic control conduit.
When test equipment is utilized which is manipulated by tubular rotation, such prior art valve mechanisms are not acceptable for use because of considerable tubular rotation which would, in turn, require additional length of exterior control conduit. Additionally, such an exterior control conduit would become wrapped around the exterior of the tubing string, leading to possible breaks and failure of tubing integrity.
The present invention obviates the problems of prior art test tree valve mechanisms when incorporated with test equipment requiring tubular rotation for activation, by providing a test tree valving mechanism which is mechanically latched into the drill string and which manipulates the valving mechanism between opened and closed positions by tubular rotation. Additionally, the apparatus provides auxiliary hydraulic means for manipulation of the valving mechanism to the closed position from the open position, as well as unlocking of the latching mechanism, in the event of a well catastrophe or other emergency when there is insufficient time to manipulate the drill string, or when the drill string is prevented from being manipulated, the auxiliary means not requiring an exterior fluid conduit, and being operational by tubing pressure, alone.